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Trapezoidal & Free Form Video Crop

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Is Trapezoidal & Free Form Video Crop possible with VideoPad Video Editor?

Example: some times uploaders to You Tube just use a video camera to film the tv, they hold the camera at an angle to avoid flair, resulting in a trapazoidal frame of their tv screen. if you down load their video it not rectangular and needs to be corrected.

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The crop effect is rectangular. There is no provision to make opposite sides of the rectangle of different lengths. You can however create a mask that will outline the trapezoidal shape of the foreshortened TV screen and then make the outer area transparent which will have a similar effect. The difficulty here is that the image remains  distorted due to foreshortening and I don't think there is a correction for this. Might be worth suggesting NCH include such an effect.


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Thanks Nat for reply.

In the example I gave its even more complicated to fix screen in post as the video cameras are often hand held with no gimbals or steady cam type devices and often only standard HD 1920x1080 resolution.  The resulting uploaded video is shaky up & down and left to right as well as rotation.

I first try to stabilize, then use the mask but still end up with a trapezoidal screen shape if I want the screen in proportion. If I then try to use scale I turn circles into ovals, heads become noticeable wider as I scale the screen linear wider to make it rectangular.

When I watch it thru I still have the on-screen action moving out side the screen. So the left to right movement of the camera is quit a lot and irregular.

About the only think that I can do is tight crop which is cutting too much out.

Everyone that films anything should use either a steady cam type device or a rest, if you really want to film the tv to post and show people and you don’t have a tripod just use a chair to rest your video camera on and point it straight in front of the tv and don’t touch it until the item on the tv finishes. Other wise if you hand hold the video camera you will make your audience sea sick with a jerky and rolling picture.

Various video editors do have tracking plug-ins, but even these are only good for scenes, locking on to something in the scene to center or other wise setting the screen frame.

There is also “tracker-pod” web camera software used in competition ballroom dancing to follow a particular couple around the ballroom floor.


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Hi pc

The Virtual Dub  de-shaker plugin that VP uses can handle quite a lot of shake as well as rotation but needs some experience in setting the different parameters to achieve the best effect. The info to do this is here....


VP will allow the user to set parameters for the two passes but in general the default setting do a good job although borders might need to be trimmed off.

As for using any of the effects like Mask,Scale and Crop etc. Although you can, as you have found, elongate and deform the image vertically or horizontally the trapezoidal foreshortening effect can't be corrected. However  c-major has filed a  a suggestion which means such an effect might be forthcoming in some future release.


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Nat thanks for comments & link on Virtual Dub’s Deshaker Plug-in.

Yes I have used it before in Virtual Dub, often tricky to setup if you don’t use the default settings.

I still don’t know why people occasionally use video cameras to film tv screens,  you are always going to get a poor results in picture and sound, especially picture due to tv line frames.

 Tv & film or video cameras don’t work together. Just learn to use PVR most tv ‘s have them now days, or if your at a convention / exhibition / stadium where there are tv screens of products & services, maybe ask if they have the videos on their website to download.


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